perception Flashcards
perception includes:
visual perception
audition
touch
pain
world to visual signal in brain
signal of 400-700mm for brain to process and encode
photoreceptors convert light wave energy into neural signal
- light energy –> neural activity
structure and function of the eye
Retina
- image on the retina is flipeed upside down and backwards
- light wave energy into back surface of eye
- shadows and disruptions are not seen
photoreceptor specialised function
first stage of information processing
2 photoreceptor types
Cones
Rods
RODS
work in dim lighting
- sensitive to movement but not fine detail or colour
- in dim lighting no colour, cone photoreceptors can’t work
* found in the periphery
CONES
function and location
work in good lighting and are sensitive to fine detail and colour
* interpret colour detail
* predominately found at the fovea
* at the fovea - 170 thousand receptors per mm^2
Visual acuity
ability to see fine detail
- this is determined by the properies of rods and cones
- no light receptors when blinking
context for vision
C + C
- colour contrast - colours we perceive are influenced by its surrounding
- colour constancy - tendency of a surface to appear the same colour under range of illuminants
* need to discount the illuminant (light) and determine true colour
light sources - bent shape, colours to different, creates shadow
retinal image to recognisable objects
- visual info seen on right of fixation is processed in left of brain
- visual info on left of fixation is processed on right
of brain
primary visual cortex
V1
first stage of cortical (visual processing)
- involved with the coding of lines and edges in visual scene
cortical cell sensitive to orientation
rules for visual cues
4 gestalt principles
linking oriented lines to outline shapes
- organise images into figures of interest and background = figure ground segregation
* similarity
* proximity
* closure
* continuity
Similarity
Proximity
Closure
Continuity
2 cues
depth of vision
- monocular cues
- binocular cues
M
- linear perspective
tendency for lines to converge when parallel
further away = smaller
eg. train tracks
2 interposition/occlusion
cue to relative depth order
one object can obstruct the view of part of another object
3 relative heights
- distant objects are seen as smaller and higher in relation to items that are closer.
Relative to horizon
Closer to horizon - further away
4 clarity
Depth cue based on that light is scattered by the atmosphere
More light is scattered when we look through more atmosphere
More distant objects appear fainter, bluer, and less distinct
5 Relative size
comparison of size between items
- if all equal, assume smaller objects are further than larger ones
-
6 motion parallax
Images close to the observer move faster across the visual field that images farther away
binocular clarity
- each eye has different view
- where we are not looking, the brain sees double (fovea)